The present invention relates to surveillance systems and apparatus used to prevent shoplifting and similar unauthorized removal of articles from a controlled area. More particularly, it relates to apparatus for deactivating a surveillance tag for authorized removal from the area.
In U.S. Pat. No. 4,063,229, issued on Dec. 13, 1977 to John Welsh and Richard N. Vaughan for "Article Surveillance", and assigned to the same assignee as the present application, there is described a system wherein sensor-emitter labels or tags containing a semiconductor diode or the like are applied to an article for the purpose of surveillance. For deactivating such tags, the patent describes various devices including, among others, radio frequency generators for burning out the diode.
Said Pat. No. 4,063,229 also describes the construction of special tags containing layers of ferrite material that can be magnetized or demagnetized by a suitable magnetic field for altering the operating characteristics of the tag and thereby deactivating the same.
A further approach to tag deactivation is shown in an "Apparatus For Deactivating A Surveillance Tag" as disclosed in U.S. Pat. No. 4,318,090, issued on Mar. 2, 1982 to Douglas A. Narlow and Eugene Stevens and also assigned to the same assignee as the present application.
Said Pat. No. 4,318,090 discloses a wand-like probe with spaced contacts arranged to be applied to and drawn along the surface of a surveillance tag that contains a diode semiconductor with exposed surface terminals. When the probe contacts engage the diode terminal, alternating current in the form of an RF signal is passed through the diode sufficient to destroy its unidirectional conducting characteristics and thereby deactivates the tag. However, production tolerances at times permit the manufacture of surveillance tags with misaligned or defective surface terminals. Such misalignment occasionally prevents the contacts of the probe described in Pat. No. 4,318,090 from conductively engaging the diode terminals, thus preventing the deactivation of the tag, an undesirable result. Moreover, the cost of these disposable tags is an important factor in their success, and the need to lessen such cost is readily apparent. The need to produce exposed external, perfectly aligned contacts on a surveillance tag increases the cost significantly.
Thus, it is an object of the present invention to overcome the disadvantages inherent in the previously known surveillance systems while actually decreasing the cost of the expendable tags utilized.
It is a further object to provide a more reliable and safer deactivating system employing a non-contact probe.